1.2 The Periodic Table

Figure 1 shows the melting points of the Group 1 elements.

Figure 1

Describe the trend in melting point as you go down Group 1 in the Periodic Table.

Estimate the melting point of potassium (K).

The atoms in a metal are held together by metallic bonds.

Describe how the strength of the metallic bonds in the elements changes as you go down Group 1.

Use your knowledge of how metallic bonds form to suggest a reason for the trend in the melting points of the Group 1 elements.

The compound sodium chloride, NaCl, is made when two elements in Period 3 of the Periodic Table react.

For each of the elements in sodium chloride:

[1]

[2]

Complete the table using the Periodic Table.

Sodium chloride is made up of ions.

Explain how these ions form.

Give the electronic configuration of:

[1]

[1]

Mendeleev devised a Periodic Table in 1869.

It is shown in Figure 1.

Figure 1

Mendeleev ordered the elements in terms of their atomic mass.

[1]

[4]

Mendeleev reversed the order of some of the elements.

For example, he put tellurium, which has an atomic mass of 128 before iodine, which has an atomic mass of 127.

[1]

[1]

Mendeleev left some gaps, shown by the shaded areas.

Explain why he did this.

At the time, many other scientists did not accept Mendeleev’s Periodic Table.

Suggest two reasons why.

Figure 1 shows one group from Mendeleev’s Periodic Table from 1869.

 
Figure 1

Eka-aluminium is the name that Mendeleev gave to an undiscovered element. This element is now known as gallium.

Gallium has the atomic number 31.

State two things that this number tells you about gallium atoms.

Mendeleev was able to make some predictions for the properties of gallium.

These are shown in Figure 2.

Figure 2

Explain why he was able to make these predictions.

Estimate the relative atomic mass of gallium.

Gallium was discovered in 1875.

Suggest why the discovery of gallium convinced other scientists that Mendeleev’s Periodic Table was correct.

In Figure 8, the letters A, E, G, J, X and Z show the positions of six elements in the periodic table.

These letters are not the symbols of the atoms of these elements.  

Figure 8

Using the letters A, E, G, J, X and Z

Element E has an atomic number of 5.
In a sample of E there are two isotopes. One isotope has a mass number of 10 and the other isotope has a mass number of 11.

(2)

Element X has an atomic number of 18.

State the electronic configuration of an atom of element X. 

In an experiment, 3.5 g of element A reacted with 4.0 g of element G to form a compound.

Calculate the empirical formula of this compound.
(relative atomic masses: A = 7, G = 16)

You must show your working. 

An oxygen atom has six electrons in its outer shell.

A hydrogen atom has one electron in its outer shell.

Complete the dot and cross diagram of a molecule of water, H₂O.

Show outer shell electrons only.

An element has the configuration 2.8.3. 

Which group and period is this element in?

Mendeleev arranged the elements in order of atomic mass. 

He then reversed the order of some pairs of elements. 

Why did he do this?

Figure 1 below shows the periodic table Mendeleev produced in 1869.

His periodic table was more widely accepted than previous versions

Figure 1 

The atomic weight of iodine (I) is 127 and that of tellurium (Te) is 128.

Why did Mendeleev reverse the order of these two elements?

Why did Mendeleev leave gaps for undiscovered elements?

Name the particle that allowed the elements to be arranged in order of their atomic number in the modern Periodic Table.

Mendeleev's periodic table shows lithium, sodium and potassium all in the same column. 

These elements are in the same column, Group 1, of the modern periodic table. 

Explain the reactivity of these elements going down Group 1.